The invention relates to the arranging of mobile-to-mobile connections in a wireless telecommunications system, more particularly to the arranging of mobile-to-mobile connections in wireless telecommunications systems comprising radio access gateways.
Office information systems are conventionally implemented by providing separate networks for telephone networks and for telecommunications networks comprising computers and their peripherals, i.e. typical local area networks. The development of data and telephone networks and their convergence, on one hand, and the costs arising from the building and maintenance of two parallel networks, on the other, have led to the development of systems that allow local area networks to be used for providing services provided by telephone networks. This trend is essentially due to the improved applicability of IP technology, which has traditionally been employed in data networks, to the transmitting of telephone services.
Modern office telecommunications systems allow also mobile communications systems to be connected to operate through a local area network. In such cases the Local Area Network (LAN), which typically employs IP technology, is used for connecting speech connections based on a mobile communications system protocol to Mobile Stations (MS) via an office-specific Base Station (BS), for example. This means that the conventional Private Branch Exchange (PBX) of the office can be bypassed, and that broadband connections and excellent quality of speech can be provided with wireless data transmission also on short distances. Through the office-specific base station and the local area network the mobile stations provide a wireless connection both to other mobile stations of the office and, through a Mobile Switching Centre (MSC), to external terminals, such as mobile stations outside the office system or to terminals of the wired telephone network (Public Switched Telephone Network, PSTN).
A wireless access network is typically connected to operate through the IP network by using radio access gateways (RAGW) which transmit data between a circuit-switched wireless access network and a packet-switched IP-based network. Radio access gateway is a general term for a device carrying out the protocol conversion of the data to be transferred between the protocol used in the wireless network and that used in the IP network. It should be noted that hereinafter the term ‘data transfer’ may include the transfer of one or more types of media (audio, video, data).
In prior art wireless telecommunications systems comprising radio access gateways, an IP layer is always allocated to the connection used by a mobile station, even if the connection's source address in the radio access gateway were the same as its destination address. The addresses are the same when a mobile-to-mobile connection is concerned and both the mobile stations are served by base stations connected to the same radio access gateway. To maintain two IP protocol stacks for such connections is unnecessary, and it causes processing capacity to be wasted. The conversion of the data flow of the wireless access network to the transmission format required by the IP network and back to the transmission format of the wireless network delays the data transfer, which is particularly harmful to time-critical applications and loads the network unnecessarily.